Field Guide · protocol

Also known as: ERMES, European Radio Message System

ERMES (the European Radio Message System) is a high-speed paging standard developed by ETSI to give Europe a single, roaming-capable paging technology. It transmits at 6250 bps using 4-FSK — four-level frequency-shift keying — and is frequency-agile, letting a pager hop across a block of channels to follow its messages.12

frequency → · 16 channels in the 169 MHz band pager follows the data as it hops channels 4-FSK · 6250 bps
ERMES is frequency-agile: a pager retunes across a block of 25 kHz channels to keep receiving its 4-FSK data stream.

Overview

ERMES organises transmissions into a repeating cycle of sequences and batches so that a pager knows exactly when and where its address will appear, allowing it to sleep between its slots for long battery life. The four-level FSK doubles the bits-per-symbol over the two-level FSK of POCSAG, while forward error correction and interleaving protect the data against fading. The frequency-agile design spreads one logical service across up to sixteen 25 kHz channels in the 169.4–169.8 MHz band, so capacity scales and pagers can follow traffic across the block.

Technical characteristics

Property Value
Modulation 4-FSK (four-level)
Bit rate 6250 bps
Band 169.4–169.8 MHz
Channels Up to 16 × 25 kHz, frequency-agile
Structure Slotted sequences and batches
Coding Forward error correction + interleaving

The slotted, frequency-agile structure is what distinguishes ERMES from the simpler asynchronous POCSAG format and lets it reach much higher throughput.

History

ETSI developed ERMES in the early 1990s as its attempt to standardise European paging the way GSM standardised cellular, competing with the American FLEX high-speed paging family and the ubiquitous POCSAG. Though technically capable, it saw limited uptake, and a common European roaming paging market never fully materialised.

Deployment

A handful of ERMES services operated across Europe in the 1990s and 2000s before mobile phones and SMS eclipsed dedicated paging. Most have since closed, making live ERMES rare compared with POCSAG, which persists in hospital and emergency use.

Decoding it with GopherTrunk

GopherTrunk does not decode ERMES. Its paging support centres on the common codes POCSAG and FLEX; ERMES is documented here for identification and to round out the paging landscape. GopherTrunk decodes clear traffic only, and ERMES is not currently a supported target.

Sources

  1. ERMES — Wikipedia, for the ETSI European Radio Message System, its 4-FSK modulation at 6250 bps, and its frequency-agile 169 MHz operation. ↩

  2. Radio paging — Wikipedia, for the place of ERMES among paging standards alongside POCSAG and FLEX. ↩

See also